<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>变量</title>
</head>
<body>
    
</body>
<script>
    console.log(parseInt(""));//返回NaN
    console.log(parseInt(3.14));//返回3
    console.log(parseInt("4.12"));//返回4
    console.log(parseInt("abc123"));//返回NaN
    console.log(parseInt("123abc"));//返回123
</script>
</html>